Christopher is 5 times as old as Ashley and is also 8 years older than Ashley. How old is Ashley?
Answer: We can use the given information to write down two equations that describe the ages of Christopher and Ashley. Let Christopher's current age be $c$ and Ashley's current age be $a$ $c = 5a$ $c = a + 8$ Now we have two independent equations, and we can solve for our two unknowns. Since we are looking for $a$ , and both of our equations have $c$ alone on one side, this is a convenient time to use elimination. Subtracting the second equation from the first equation, we get: $0 =$ $5a$ $-$ $ (a + 8)$ which combines the information about $a$ from both of our original equations. Solving for $a$ , we get: $4 a = 8$ $a = 2$.